The present invention relates to a dry etching technique, and in particular to an anisotropic dry etching method that is employed in the semiconductor field for the delicate processing of thin film layers, and an apparatus therefor.
In accordance with increases in the storage densities provided for semiconductor memories, such as DRAMs, the widths of lines in thin film layers deposited on semiconductor substrates have become narrower, and at present, methods are being pursued by which to provide lines having widths of 0.1 micron or less.
Concomitantly, there is a demand for an improvement in the preciseness available with anisotropic dry etching, which is used for the delicate fabrication of a thin film layer, i.e., an improvement on the accuracy provided by etching performed perpendicular to the substrate, while the occurrence of etching parallel to the substrate is reduced to the minimum possible.
In response to this demand, for improved etching properties, a conventional anisotropic dry etching technique now employs the force of an electric field or of a magnetic field to increase the velocity of charged particles traveling perpendicular to a substrate containing reactive ions, such as fluorine ions.
However, with this method, damage incurred to a semiconductor layer due to the reactive ions is increased in accordance with the increase in the kinetic energy of the reactive ions, and either a defect will occur in the layer, or the quality of the layer will be altered.
To resolve the conventional problems, it is one object of the present invention to provide an accurate dry etching technique having no adverse or damage producing effect.
It is another object of the present invention to provide a new dry etching technique that employs a particle flow and a light beam, especially a flow of neutral radicals and a light beam.
To achieve the above objects, according to the present invention, a dry etching method comprises the steps of: preparing an object to be etched; preparing a flow of neutral radicals; irradiating the flow of neutral radicals with a light beam to impart a change in the velocity component of the neutral radicals parallel to the surface of the object to be etched; and etching the object to be etched while the object to be etched is exposed to the flow of the neutral radicals whose parallel velocity component has been altered.
Further, according to the present invention, a dry etching apparatus comprises: a vacuum container; an object table provided in the vacuum container to hold thereon an object to be etched; a neutral radical flow source, located at a position opposite the surface of the object table on which the object to be etched is mounted, for emitting a flow of neutral radicals directed toward the object to be etched mounted on the object table; and a light beam source, located between the object table and the neutral radical flow source, for emitting a light beam to irradiate the flow of the neutral radicals emitted by the neutral radical flow source to impart a change in the velocity component of the neutral radicals parallel to the surface of the object to be etched.
More specifically, a dry etching method comprises the steps of: preparing an object to be etched; preparing a flow of neutral radicals; irradiating the flow of neutral radicals with a light beam so that their velocity component parallel to a surface of the object is reduced; and exposing the flow of neutral radicals whose parallel velocity component is decreased as it approaches the object and upon impact, etching the object.
In addition, according to the present invention, a dry etching apparatus more specifically comprises: a vacuum container; an object table provided in the vacuum container on which to mount thereon an object to be etched; a radical flow source, located at a position opposite the surface of the object table on which the object to be etched is mounted, for emitting a flow of neutral radicals toward the object to be etched mounted on the object table; and a light beam source, located between the object table and the radical flow source, for irradiating a light beam toward the flow of the neutral radicals emitted by the radical flow source, so that the velocity component of the neutral radicals parallel to the surface of the object to be etched is negligible compared to the velocity component perpendicular to the surface.